Enum Event 

pub enum Event {
    OnStart {
        runnable: String,
        run_id: Uuid,
        input: Value,
    },
    OnNodeStart {
        node: String,
        step: u64,
        run_id: Uuid,
    },
    OnNodeEnd {
        node: String,
        step: u64,
        output: Value,
        run_id: Uuid,
    },
    OnLlmToken {
        token: String,
        run_id: Uuid,
    },
    OnToolStart {
        tool: String,
        args: Value,
        run_id: Uuid,
    },
    OnToolEnd {
        tool: String,
        result: Value,
        run_id: Uuid,
    },
    OnError {
        error: String,
        run_id: Uuid,
    },
    OnEnd {
        runnable: String,
        run_id: Uuid,
        output: Value,
    },
    OnCheckpoint {
        step: u64,
        run_id: Uuid,
    },
    Custom {
        kind: String,
        payload: Value,
        run_id: Uuid,
    },
}

A structured event emitted by stream_events() — exposes per-step graph activity, tool calls, token deltas, and errors.

Variants

OnStart

A Runnable started.

Fields

runnable: String

Name of the runnable that started.

run_id: Uuid

Correlation ID for this run.

input: Value

Serialized input value.

OnNodeStart

A graph node started.

Fields

node: String

Node name.

step: u64

Superstep number.

run_id: Uuid

Correlation ID for this run.

OnNodeEnd

A graph node finished.

Fields

node: String

Node name.

step: u64

Superstep number.

output: Value

Serialized output value.

run_id: Uuid

Correlation ID for this run.

OnLlmToken

LLM emitted a token.

Fields

token: String

The token text.

run_id: Uuid

Correlation ID for this run.

OnToolStart

Tool execution started.

Fields

tool: String

Tool name.

args: Value

Serialized arguments.

run_id: Uuid

Correlation ID for this run.

OnToolEnd

Tool execution finished.

Fields

tool: String

Tool name.

result: Value

Serialized result.

run_id: Uuid

Correlation ID for this run.

OnError

A Runnable errored.

Fields

error: String

Error description.

run_id: Uuid

Correlation ID for this run.

OnEnd

A Runnable finished successfully.

Fields

runnable: String

Name of the runnable that finished.

run_id: Uuid

Correlation ID for this run.

output: Value

Serialized output value.

OnCheckpoint

A graph engine persisted a checkpoint at a superstep boundary.

Fields

step: u64

Step number that was just persisted.

run_id: Uuid

Correlation ID for this run.

Custom

User-emitted event from a graph node via NodeCtx::write_custom. Carries an arbitrary kind label and a JSON payload — the consumer decides how to interpret it. Used by StreamMode::Custom to surface node-authored progress signals without cluttering the typed enum.

Fields

kind: String

Caller-defined label (e.g. "progress", "chunk").

payload: Value

Arbitrary JSON payload.

run_id: Uuid

Correlation ID for this run.

Trait Implementations

impl Clone for Event

fn clone(&self) -> Event

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Event

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Event

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for Event

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.